(a) Field of the Invention
The present invention relates to a thermal spray coating material, and more particularly, the present invention relates to a multi-component thermal spray coating material which is used for parts of equipment used in corrosive environments found in semiconductor or display manufacturing equipment, chemical plants, power plants, etc.
(b) Description of the Related Art
Parts of equipment used in a corrosive environment require an excellent corrosion resistant coating in order to improve the durability of the equipment. Particularly, vacuum plasma equipment is widely used in semiconductor device processes or ultra-fine shaping processes. Examples of the use of vacuum plasma equipment include PECVD (Plasma Enhanced Chemical Vapor Deposition) equipment for forming a deposited film on a substrate by a chemical deposition method using plasma, sputtering equipment for forming a deposited film by a chemical method, and dry etching equipment for etching a substrate or a material coated on the substrate into a desired pattern.
The vacuum plasma equipment etches a semiconductor device or forms an ultra-fine shape by using high-temperature plasma. As such, high-temperature plasma is generated within the vacuum plasma equipment, thus easily damaging a chamber and internal parts thereof. Moreover, since particular elements or contaminant particles are generated from surfaces of the chamber and parts, there is a high possibility of contaminating the interior of the chamber.
Especially, in the case of the plasma etching equipment, a reactive gas containing F and Cl is injected under a plasma atmosphere, causing inner walls of the chamber and the internal parts to be exposed to a severely corrosive environment. Such corrosion primarily damages the chamber and the internal parts and secondarily generates contaminants and particles, causing an increase in a defect rate and degradation of products generated through a process within the chamber.
A vacuum plasma chamber and internal parts are selected in consideration of various characteristics, such as corrosion resistance, processability, ease of fabrication, price, insulation properties, etc. As a material of the vacuum plasma chamber, a metallic material such as a stainless alloy, aluminum (or an alloy thereof), or titanium (or an alloy thereof), etc., or a ceramic material such as SiO2, Si, Al2O3, etc. is generally used. Preferably, the chamber is fabricated in an integral manner by casting, etc and then internally processed. Otherwise, the chamber may be fabricated by processing a number of parts and then assembling them, in consideration of productivity and manufacturing cost. For parts made of an Al alloy, a method in which an Al2O3 ceramic coating film is formed on a surface of a base material through an anodizing process is commonly employed. However, the ceramic coating film formed by this method has many defects therein, so it is difficult to expect high hardness and corrosion resistance and contaminant particles are generated at high rates.
For a variety of other metallic materials and ceramic materials to which the anodizing process is hardly applicable, a method of forming a protective film by using materials having high corrosion resistance to outside exposure and a low generation rate of contaminant particles (e.g., Al2O3, Y2O3, ZrO2, AlC, TiN, AlN, TiC, MgO, CaO, CeO2, TiO2, BxCy, BN, SiO2, SiC, etc) is employed. Recently, a method of forming a protective film using a heterogeneous ceramic material is employed even for Al-alloy materials to which the anodizing process is applicable. One of the most representative methods for forming a protective film using a heterogeneous ceramic material is a thermal spray coating method.
Thermal spray coating usually refers to a technique in which metal or ceramic powder is injected into a high-temperature heat source and heated, and then fully molten or semi-molten powder is laminated on the surface of a base material to form a coating film. This technique is classified into plasma thermal spray coating, HVOF (High velocity oxygen Fuel) coating, and so on depending on the type of heat source. Although Al2O3 and Y2O3 are the most widespread thermal spray coating materials commercially used nowadays, their corrosion resistance is not excellent and this leads to problems such as shortening the lifespan of parts and forming reaction products on the surfaces of the parts.
Meanwhile, the inventors of the present invention have recently suggested a novel technique regarding a new coating material that substantially overcomes the aforementioned problems of the ceramic thermal spray coating material and a coating method thereof. They have succeeded in forming the most part (50% or more, preferably, 100%) of a coating film in an amorphous phase by coating a multi-component ceramic material having three or more constituent elements by thermal spraying [Korean Patent Registration Nos. 10-0940812, 10-0939256, and 10-1101910]. Korean Patent Registration Nos. 10-0940812 and 10-0939256 suggested a patented technology that greatly improves corrosion resistance, as compared to conventional Y2O3 coatings, by mixing Al2O3 fine powder and Y2O3 fine powder into composite powder having an average diameter of 40 to 60 micrometers and then thermally spraying it to make the entire or most part of a coating film amorphous. Plasma corrosion resistance was greatly improved as shown in the following Table 1,
TABLE 1Al2O3Y2O3Al—Y—OcoatingcoatingcoatingMicrohardness(Hv)800-850300-500700-750Scratch Resistance110(Ext.)-22(Int.) 1.2(Sc. Depth, mm)Corrosion Resistance−00.550.99-0.11in 2N HCl (Δg/g)ICP plasma etching4.6321.2130.215resistance againstF(μm/hr)Dielectric constant—1267(thin film)1254(thin film15.1 (10 KHz)-16.1 (10 KHz)-11.9 (1 MHz)12.1 (1 MHz)(bulk)(bulk)Defectsmanyvery manyalmost none(Splat boundaries, pores)
Korean Patent Registration No. 10-1101910 suggested a technology which further improves corrosion resistance to CI gas-containing plasma by preparing composite powder of Al2O3 fine powder and ZrO fine powder and then thermally spraying it to form an Al—Zr—O amorphous coating (see FIG. 1)
FIG. 2 shows the results of comparison of the etching rates of an Al—Zr—O amorphous coating and other coating materials in Cl gas-containing plasma when the coating condition is not optimally controlled. As shown in FIG. 2, the corrosion resistance of the Al—Zr—O amorphous coating is very sensitive to coating conditions. In some cases, the corrosion resistance of the Al—Zr—O amorphous coating may be higher than that of an Al—Y—O amorphous coating material under a Cl plasma gas atmosphere. That is, a coating material is coated at an applied power of 30 to 38 Kw (850 A and 45V) and a coating powder injection rate of 1.5 g/min, which is a general ceramic powder thermally spray coating condition, when argon gas and helium gas are respectively controlled at 38 L/min and 20 to 50 L/min to form plasma using an SG-100 plasma gun. Such a coating material shows a higher etching rate than the Al—Y—O amorphous coating.
The above-mentioned technology is to form the most part (50% or more, preferably, 100%) of a coating film in an amorphous phase by thermally spraying a multi-component ceramic material having three or more constituent elements. By doing so, volumetric shrinkage, which occurs when molten liquid droplets colliding with the surface of the base material are cooled and turn into a solid state upon thermal spray coating, is minimized. As a result, the formation of cracks, splat boundary gaps, and pores, which inevitably appear upon ceramic thermal spray coating, can be minimized, thereby enhancing the characteristics of the coating film.
Even though the aforementioned amorphous coating material has been greatly enhanced in plasma corrosion resistance, compared to conventional coating materials, it is still fragile in a process using corrosive Cl group-containing gas. Especially in recent years, there is a demand for higher corrosion resistance in process conditions in order to increase the production rate of semiconductor devices/displays. This creates a need for a new material technology which can further enhance corrosion resistance.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.